concentric loads

[Arnie]

Did i spell that right ? Any way i have a good question about this subject .Why when i check 50 cases they are within .001 or less out of round and when i load 50 bullets from a Paul Jones Mould i get a little less than one third that are .001 or less out ,then about another third about .002 and then another less than one third about .003 out and then about 7 or 8 are about .005 or .006 out of concentric .This is with about .0015 neck tension on 20-1 alloy in BP loads .Arnie

[44man]

I think you are doing very good. It depends on the brass itself. Some of your case necks might just be thicker on one side. Sort out the ones with too much runout and use them for general shooting. .003" and less should be OK for silhouette.
Now with a bottle neck, most damage is done by over sizing and expanding too much. Shoulders get bent.

[Dale53]

Arnie;
One thing for sure, you have proper neck tension (my standard for BPCR-Sil, is .001"-.002" case neck tension.

I, also, believe it is uneven case necks...

Dale53

[charger 1]

Typically what I do (for what its worth) Is shoot bigger bores 40+, Get them as concentric as possible. Although your doing very well,You'd notice that even get more true if your expander took the neck to where you just barely needed the press, just a bit more pressure than can be done by thumb. When I do 45 rifle stuff it's almost size for size,maybe a couple tenths of interference. Then to totally get rid of any runout that could effect accuracy on firing I like long tight throats to line things up. Stay away from the lee wobble plug expander. If you have lee stuff thats fine, but get an expander die withb a solid button thats only a couple tenths smaller than boolit

[Buckshot]

...........Some of your off axis boolits could be due to simple mechanics. This can be one or several things. Seater punch, case leaning, seam protruding a bit more on one side of the boolit then the other (on occasion). The casemouth expander may be expanding casemouths off axis, or flaring unevenly. The fact that the case can tip slightly in the shellholder and allow the boolit to be seated 'off' a bit can contribute.

.............Buckshot

[trk]

Did i spell that right ? Any way i have a good question about this subject .Why when i check 50 cases they are within .001 or less out of round and when i load 50 bullets from a Paul Jones Mould i get a little less than one third that are .001 or less out ,then about another third about .002 and then another less than one third about .003 out and then about 7 or 8 are about .005 or .006 out of concentric .This is with about .0015 neck tension on 20-1 alloy in BP loads .Arnie


Yes, you spelled it right. Here in America we use two terms interchangably, but concentric refers to two things having the same center where coaxial refers to two things having the same axis. (Circles have centers, cylinders have axes.)

The alignment of the bullet and the case is critical to having an assembly where the bullet and case are coaxial.

Several methods are used to do this, some better than others.

Several techniques are often used to help alignment as well.

The variation you describe is typical of any manufacturing process - and what you're describing is ammunition loaded better than most commercial ammo.

Some seating dies have a sliding support to align the bullet and the case.

Some seating dies are operated by hand and have a 'chamber' that closely fits the sized case and precisely seats the bullet by hand or with a small arbor press.

Some folks will slightly loosen the seating die in the press to help alignment, and some folks will seat the bullet half way and then rotate the bullet 180 degrees and fully seat it.

Measuring (as you're doing) is a great way to determine which technique works best.

Don't forget to correlate the level of accurate axial alignment with how well it does or does not shoot!

Army marksmanship FM's show graphs of match vs ball ammo and the distribution of runout (an indicator of axial alignment). Match ammo typically is .001 to .002" runout and ball ammo worse. It's not uncommon to find commercial ammo running from .002 to .010" in the same box with most being .005 - .007".

Keep good notes - that will help you improve over time.

[Arnie]

This Question is on a 35/40 Maynard caliber with a very tight chamber .I used 38/55 cases and formed them in CH dies designed by Dan .The reamer was designed by Dan Theodore and i have the necks turned to .0085 . Like i said ,the cases all show very good numbers but not all the bullets load properly. I am using the CH dies to seat the bullets .Maybe i should send a few cases to some one that makes the seating dies that have the sliding sleeve that has the side port . I guess it is possible that the bases of some of these cases could be slightly off . I will have to try rotating the cases as i seat the bullet to see if less of them have bad run out . Thanks for all the ideas ,Arnie

[John Boy]

I will have to try rotating the cases as i seat the bullet to see if less of them have bad run out .
Arnie: The 180 degree twisting of the case when seating the bullets does work. The big name gun cranks are always debating the virtues of which micro dial seater is best for best concentric alignment.

With mouth chamfering only, using non custom brass in multiple calibers, when I measure loaded rounds with the dial comparator ... they are 99% within 0.002 using the 180 twist method. I've even done the 90 degree twist and it's no better than the 180